[FFmpeg-devel] [PATCH] fftools/ffmpeg_mux_init: do not write encoder metadata for ogg files with bitexact

[FFmpeg-devel] [PATCH] fftools/ffmpeg_mux_init: do not write encoder metadata for ogg files with bitexact

[Tolga Celebi via ffmpeg-devel]

From: tolgakaan12 <70590077+tolgakaan12@users.noreply.github.com>

The set_encoder_id function in fftools/ffmpeg_mux_init was writing a shortened encoder tag even when -bitexact flag was set, instead of omitting it entirely like other formats (flac, mp3, wav) do. This patch makes the function return early if bitexact flag is set, ensuring no encoder metadata is written.

Fixes ticket #11656.
---
 fftools/ffmpeg_mux_init.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fftools/ffmpeg_mux_init.c b/fftools/ffmpeg_mux_init.c
index bcbbee9126..3d13c9c257 100644
--- a/fftools/ffmpeg_mux_init.c
+++ b/fftools/ffmpeg_mux_init.c
@@ -1167,15 +1167,15 @@ static int set_encoder_id(OutputStream *ost, const AVCodec *codec)
     uint8_t *encoder_string;
     int encoder_string_len;
 
+    if (ost->file->bitexact || ost->bitexact)
+        return 0;
+
     encoder_string_len = sizeof(LIBAVCODEC_IDENT) + strlen(cname) + 2;
     encoder_string     = av_mallocz(encoder_string_len);
     if (!encoder_string)
         return AVERROR(ENOMEM);
 
-    if (!ost->file->bitexact && !ost->bitexact)
-        av_strlcpy(encoder_string, LIBAVCODEC_IDENT " ", encoder_string_len);
-    else
-        av_strlcpy(encoder_string, "Lavc ", encoder_string_len);
+    av_strlcpy(encoder_string, LIBAVCODEC_IDENT " ", encoder_string_len);
     av_strlcat(encoder_string, cname, encoder_string_len);
     av_dict_set(&ost->st->metadata, "encoder",  encoder_string,
                 AV_DICT_DONT_STRDUP_VAL | AV_DICT_DONT_OVERWRITE);
-- 
2.50.1 (Apple Git-155)

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[FFmpeg-devel] Re: [PATCH] fftools/ffmpeg_mux_init: do not write encoder metadata for ogg files with bitexact

[Gyan Doshi via ffmpeg-devel]

On 2025-11-16 04:02 am, Tolga Celebi via ffmpeg-devel wrote:
> From: tolgakaan12 <70590077+tolgakaan12@users.noreply.github.com>
>
> The set_encoder_id function in fftools/ffmpeg_mux_init was writing a shortened encoder tag even when -bitexact flag was set, instead of omitting it entirely like other formats (flac, mp3, wav) do. This patch makes the function return early if bitexact flag is set, ensuring no encoder metadata is written.
>
> Fixes ticket #11656.

NAK. Bitexact does not mean lack of encoder metadata - it means metadata 
that is invariant across versions. Most formats will still write some 
encoder metadata.
This patch fails close to 200 of our automated tests - see 
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20251115223242.90376-1-celebitolgakaan@gmail.com/

To omit this for a particular muxer, modify that muxer by checking for 
the flag AVFMT_FLAG_BITEXACT. Look at libavformat/wavenc.c for reference.

Regards,
Gyan


> ---
>   fftools/ffmpeg_mux_init.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fftools/ffmpeg_mux_init.c b/fftools/ffmpeg_mux_init.c
> index bcbbee9126..3d13c9c257 100644
> --- a/fftools/ffmpeg_mux_init.c
> +++ b/fftools/ffmpeg_mux_init.c
> @@ -1167,15 +1167,15 @@ static int set_encoder_id(OutputStream *ost, const AVCodec *codec)
>       uint8_t *encoder_string;
>       int encoder_string_len;
>   
> +    if (ost->file->bitexact || ost->bitexact)
> +        return 0;
> +
>       encoder_string_len = sizeof(LIBAVCODEC_IDENT) + strlen(cname) + 2;
>       encoder_string     = av_mallocz(encoder_string_len);
>       if (!encoder_string)
>           return AVERROR(ENOMEM);
>   
> -    if (!ost->file->bitexact && !ost->bitexact)
> -        av_strlcpy(encoder_string, LIBAVCODEC_IDENT " ", encoder_string_len);
> -    else
> -        av_strlcpy(encoder_string, "Lavc ", encoder_string_len);
> +    av_strlcpy(encoder_string, LIBAVCODEC_IDENT " ", encoder_string_len);
>       av_strlcat(encoder_string, cname, encoder_string_len);
>       av_dict_set(&ost->st->metadata, "encoder",  encoder_string,
>                   AV_DICT_DONT_STRDUP_VAL | AV_DICT_DONT_OVERWRITE);

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